1997 GMC C1500 Truck won't start

Hi, I'm writing because my truck started yesterday and but when I put it in drive and backed it up, it turned off. I then turned it back on and it ran for about 10 seconds and then died again. I thought that I might be out of gas so I put some in it thinking that it would fix the problem. It didn't so I proceeded to check my fuses and they all look good. I don't own a voltage meter to check to see if the fuses have any voltage. I wanted to check the fuel relay and ignition relay but again, I don't own a voltage meter. I know that the spark plugs are in need of replacement but the truck has run just fine since I bought it in August of last year. I'm thinking of replacing the spark plugs, ignition and relay switch or the fuel pump. I have also heard that this year and model of truck has issues with the ignition switch. The engine spins the belt but won't turn over. It wants to crank but it seems that something has stopped working and won't allow it to fully turn over. What do you think is the most likely cause of this issue?